1. Field of the Invention
The present invention pertains generally to vertical takeoff and landing (VTOL) aircraft. More particularly, the present invention pertains to aircraft having tilting propulsion systems for vertical takeoff. The present invention is particularly, but not exclusively, useful as a VTOL aircraft design for relatively small remote control (RC) aircraft and larger passenger aircraft.
2. Description of the Prior Art
Vertical Takeoff and Landing (VTOL) aircraft are generally any of numerous unconventional designs for aircraft including rotary wing helicopters, having rotatable or divertible propulsion systems that allow for vertical takeoff/landing and horizontal flight. Advancements in technology have long been desired to produce a more commercially viable design for VTOL aircraft. Current methods of travel have numerous constraints, particularly conventional air travel that requires expensive airports having long runways and vast airspace. Especially, transportation between small and medium cities could benefit from major improvements in aircraft design and within large cites where automobiles and current aircraft have not met the needs of the public.
The helicopter as a VTOL aircraft was once envisioned for public use as providing safe and efficient travel unsuitable for current automobiles and typical runway aircraft. For many reasons, however, the helicopter has remained a limited-use, special-purpose aircraft. Principally, the large rotating lift blades of the helicopter design must meet very stringent mechanical requirements and require a very complicated system for drive and control. Another disadvantage of the helicopter is that the angular moment caused by the lift blades requires the use of a tail rotor rotating about a horizontal axis. Loss of the tail rotor is thus a potentially devastating casualty. Helicopters also employ pitch adjustable blades resulting in extremely expensive construction and maintenance costs and a high level of pilot proficiency in flying and controlling the aircraft.
Certain additional designs for vertical takeoff and landing (VTOL) aircraft and for vertical and short takeoff and landing (V/STOL) are well known. Some designs are modifications of fixed wing aircraft to include vertical propulsion while maintaining stability in vertical lift mode. U.S. Pat. No. 4,474,345 “Tandem Fan Series Flow VSTOL Propulsion System” by R. G. Musgrove discloses a propulsion system for V/STOL that includes a jet engine for normal wing borne flight modified with additional fans having a diverter to exhaust thrust directionally downward. While this design is capable of supersonic speeds, an aircraft of this system will be very heavy and require a relatively powerful vertical thrust. Similarly, a design proposed by Moller, U.S. Pat. No. 5,115,996 employs directional vectoring of thrust to provide vertical lift capability. This design will also yield a relatively heavy aircraft as it employs multiple engines with large horsepower requirements. Furthermore, mobility and maneuverability are concerns especially at lower air speeds and transitioning between hovering and normal flight mode.
Additional designs of VTOL aircraft are known in the art each having certain advantages and drawbacks. One such design is a tilt-rotor type that is also referred to a “convertible” type, having rotors, which are capable of being tilted with respect to the aircraft structure. For example, during takeoff, the rotors are orientated almost vertically so as to operate like a rotary wing, in order to allow vertical takeoff in the manner of a helicopter. Next, the aircraft flight is transitioned from vertical to horizontal mode, thus the rotors are tilted horizontally so as to operate like airscrews.
Among the tilt-rotor type VTOL aircrafts there are some that employ multiple large engines to provide the necessary thrust. These designs however will be relatively heavy and will not have a particularly attractive power-to-weight ratio. Also, in vertical flight mode, a large weight proportioned at a distance from the aircraft's center of gravity will cause a moment of inertia adversely affecting stability and mobility. Also known, are VTOL designs of model aircraft or miniature remote controlled (RC) aircraft. One such design is disclosed in U.S. Pat. No. 5,836,545 Toy Aircraft And Method for Remotely Controlling the Same by D. Dixon. In the model aircrafts, weight is relatively less of a concern and stability is of greater concern. In all designs, weight, stability and power-to-weight ratio of the propulsion system are chief design concerns.
Heretofore, existing technology in power systems and strength in lightweight materials have encumbered the realization of a commercially viable VTOL design. Particular advancements in these areas have lead to the present invention that provides a lightweight VTOL design particularly suitable for passenger aircraft or an RC model aircraft. The present invention additionally provides a VTOL design that is easy to manufacture, relatively simple to use, and comparatively cost effective.